1. Field of the Invention
The present invention relates to an information device having a function for inputting information by using means such as a pen. In particular, the present invention relates to an information device in which pen input operations are performed on a screen of a display device. The present invention relates to an EL display device using EL elements as the display device, and further, relates to electronic devices, such as portable information devices, having the information device of the present invention.
Note that, in this specification, the term EL element denotes an EL element utilizing both light emission from singlet excitons (fluorescence) and light emission from triplet excitons (phosphorescence).
2. Description of the Related Art
The demand for pen input method portable information devices has risen in terms of miniaturization and operability. The pen input method is a method for the input of information by using a specialized pen or arbitrary pen, and by either contacting pen tip to a display screen, or bringing the pen tip close to the display screen.
Namely, input of information corresponding to positions indicated by the pen tip on the display screen is performed. The display screen also functions as a pen input screen. It is necessary to specify the positions indicated by the pen on the pen input screen with this pen input method, and methods such as a resistive film method and an optical method exist as means for the pen input.
The resistive film method is explained first.
FIG. 7 is a cross sectional diagram showing the structure of a resistive film pen input device. Note that a pen input device 7711 is formed overlapping with and on the upper portion of a display device 7708. The display device 7708 has a display portion 7709 and a peripheral circuit 7710.
A movable electrode 7701 and a fixed electrode 7702 sandwich dot spacers 7704 in the pen input device 7711, and both are connected in parallel with a gap of approximately 100 to 300 μm by a lamination material 7703. The movable electrode 7701 and the fixed electrode 7702 are formed by conductive materials having transparency so that images projected on the display portion 7709 of the display device 7708 can be seen through the pen input device 7711. In general, an indium tin oxide (ITO) film is used as the conductive material having transparent properties.
The movable electrode 7701 touches the fixed electrode 7702 in a position indicated by the input pen 7704 on the pen input device 7711 with the resistive film method (input point A in FIG. 7). At this time, in the method, the position of the input point A is read out as the ratio of resistances R1 and R2 from two position detection electrodes 7706 and 7707.
Specifically, an example of performing position read out is shown in FIG. 8. A pressure is applied by an input pen 807 from a movable electrode 801 side and there is contact between the movable electrode 801 and a fixed electrode 802 at the input point A. A voltage is applied between two electrodes 803 and 804 of the movable electrode 801 here, and an electric potential gradient is generated within the movable electrode 801. By measuring the electric potential VA of the input point A at this point, resistance values Rx1 and Rx2 from the electrode 803 and the electrode 804 to the input point A can be found. If the film quality of the movable electrode 801 is assumed to be uniform, then the resistance values Rx1 and Rx2 are proportional to the distances from the electrodes 803 and 804 to the input point A, respectively.
Similarly, a voltage is applied between two electrodes 805 and 806 of the fixed electrode 802, and an electric potential gradient within the fixed electrode 802 is generated. By knowing the electric potential VA of the input point A at this point, resistance values Ry1 and Ry2 from the electrode 805 and the electrode 806 to the input point A can be found. If the film quality of the fixed electrode 802 is assumed to be uniform here, then the resistance values Ry1 and Ry2 are proportional to the distances from the electrodes 805 and 806 to the point A, respectively. The position of the input point A can thus be determined.
Note that the method of measuring the electric potential of the input point A for measuring the position of the input point A is not limited to the above structure, and various other methods can also be used.
An optical method pen input device is explained next. A schematic diagram of an upper surface of the optical method pen input device is shown in FIG. 9A.
If a pen tip of an input pen 901 makes contact to an input portion 902, the contact position is detected. The position detection operation is explained.
X-1 light emitting diodes (hereafter referred to as LEDs) 21 to 2x are arranged in a right edge portion in the periphery of the input portion 902, and x-1 phototransistors (hereafter referred to as PTs) 31 to 3x are arranged in a left edge portion of the input portion 902, opposite the LEDs 21 to 2x. The light emitting diodes and the phototransistors are embedded in a frame 4.
Y-1 LEDs 51 to 5y are arranged in a lower edge portion, and y-1 PTs 61 to 6y are arranged in an upper edge portion, opposite the LEDs 51 to 5y. The LEDs and the PTs are embedded in the frame 4.
The LEDs 21 to 2x and the PTs 31 to 3x form x-1 horizontal direction touch input lines, and the LEDs 51 to 5y and the PTs 61 to 6y form y-1 vertical direction touch input lines.
The term touch input lines refer to paths along which light emitted from the LEDs travels when input to the PTs between pairs of opposing LEDs and PTs.
Note that although PTs are used as the components having reference numerals 31 to 3x and 61 to 6y, there is no limitation associated with PTs, and other components can be freely used provided that they are photoelectric conversion elements that convert light into an electric signal.
In order to increase the directionality of light emitted from the LEDs 21 to 2x and 51 to 5x, and made incident on the PTs 31 to 3x and 61 to 6y, hole shaped slits 7 are formed in front of the frame 4 in which each of the elements is embedded.
FIG. 9B is a cross sectional diagram along a line segment a-a′ of FIG. 9A. A display device 910 is formed in a portion below the pen input device. The display device 910 is structured by a display portion 911 and a peripheral circuit 912. Differing from the resistive film method, it is possible to directly see images displayed in the display portion 911.
FIG. 9A is again referenced.
The emission of light and the receiving of light are performed one pair at a time from the edge for the pairs of opposing LEDs and PTs. This operation (hereafter referred to as scanning) is performed at the same time for the horizontal direction touch input lines and the vertical direction touch input lines in the pen input device having the above structure.
One point within the input portion 902 is indicated by the input pen 901. The input point A within FIG. 9A is indicated. Light is cutoff between two touch lines 2n to 3n and 5m to 6m at this point, and the position A at which the input pen 901 contacts is recognized.
It is necessary to mechanically change the shape of the movable electrode as information is input with the resistive film method. The movable electrode thus fatigues with repeated shape change, and there is the possibility of it being broken. This becomes an endurance problem.
Further, even if damage does not reach actual breakage, the ITO film conductivity becomes non-uniform due to repeated deformation and in the case where minute cracks on the order of micrometers in size are formed during manufacturing process. Therefore, problems in the precision of input pen location detection develop.
In addition, the display device image is read out through the two electrodes, the movable electrode and the fixed electrode. The transmittivity of the transparent electrodes is not 100% at this time, and therefore light from the display device is attenuated and brightness of the image falls, generating visibility problems with the screen. The intensity of light emitted form the display device consequently must be made stronger so as to increase the brightness of the image, and there is a problem with increased power consumption of the device.
Further, when stress opposing substrate is applied from the outside of the device, and the distance between the two electrodes, the movable electrode and the fixed electrode, becomes equal to or less than 40 μm, then a problem exists in which Newton rings appear due to an interference effect of light reflected between the two electrodes.
In addition, this is a capacitor structure in which the two electrodes are arranged in parallel, and therefore consumption is large when a battery electric power source is used. This is a large problem for portable information devices in which low power consumption is desired.
On the other hand, there are no mechanical endurance problems with the optical method pen input device because it is not necessary for the thin films to repeatedly be deformed as with the resistive film method. Further, the display device is not seen through transparent electrodes, and therefore problems with screen visibility are also few.
However, for cases where light emitted from the light emitting elements is not received in a straight line by the paired light receiving elements, there is a possibility that recognition will not be made even if the input pen or the like indicates the position.
Furthermore, it is necessary to form columns of light emitting elements and light receiving elements, slits and the like on the display device, and therefore there is a problem in that it is difficult to make the device smaller.